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pip-cache
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# Use a cache for pip
Using a download cache speeds up image builds.
Including this element in an image build causes
$HOME/.cache/image-create/pip to be bind mounted as /tmp/pip inside
the image build chroot. The $PIP_DOWNLOAD_CACHE environment variable
is then defined as /tmp/pip, which causes pip to cache all downloads
to the defined location.
Note that pip and its use of $PIP_DOWNLOAD_CACHE is not concurrency
safe. Running multiple instances of diskimage-builder concurrently
can cause issues. Therefore, it is advised to only have one instance
of diskimage-builder that includes the pip-cache element running at a
time.
The pip concurrency issue is being tracked upstream at
https://github.com/pypa/pip/issues/1141
bfca36c772